Where Japanese surnames come from
Unlike Japanese given names, Japanese surnames have fixed characters, so their meanings are reliable. The overwhelming majority are toponymic — they describe a place or a feature of the landscape where a family lived: rice fields (Tanaka, “central rice field”; Yamada, “mountain rice field”), mountains (Yamamoto, “base of the mountain”), trees (Kobayashi, “small forest”; Matsumoto, “base of the pine”) and bridges or crossings (Takahashi, Watanabe).
A recent history
Most ordinary Japanese families only adopted surnames in 1875, during the Meiji era, when they became compulsory — which is why so many are drawn simply from the local landscape. There are well over 100,000 Japanese surnames, far more than in most countries.
The wisteria connection
Several of the most common surnames end in -tō (藤, “wisteria”) — Sato, Ito, Kato — a trace of the powerful medieval Fujiwara clan, whose name also contains that character.